1. Field of the Invention
The present invention relates to a dry etching method of forming a fine pattern in manufacturing, for example, a semiconductor device, and also to a dry etching apparatus for forming such a fine pattern.
2. Description of the Related Art
Known as micro-process techniques for manufacturing semiconductor devices are microwave plasma etching, reactive ion etching, and the like. The reactive ion etching includes a method using parallel flat electrodes, a method utilizing electron cyclotron resonance (ECR), and the like.
In a conventional reactive ion etching apparatus, the upper electrode is mounted on the top of the reaction chamber, and the lower electrode, which extends parallel to the upper electrode, is located within the reaction chamber. The upper electrode has a hollow and is grounded. A gas pipe is connected to the upper surface of the upper electrode, for introducing a reaction gas into the hollow. The upper electrode has a plurality of through holes in its lower surface, through which to supply the reaction gas into the reaction chamber. A workpiece, such as a silicon wafer, is mounted on the lower electrode. The lower electrode is connected by a blocking capacitor to a high-frequency power supply. The lower electrode is surround by a baffle plate which is located within the reaction chamber, as well. The baffle plate has a plurality of through holes. An exhaust pipe is connected to the side of the reaction chamber, for exhausting the reaction gas from the reaction chamber.
To etch the workpiece, the reaction gas is introduced into the reaction chamber through the holes made in the lower surface of the upper electrode. The gas is exhausted from the chamber through the exhaust pipe, 10 thereby controlling the gas pressure within the reaction chamber. At the same time, a high-frequency power is supplied from the high-frequency power supply to the lower electrode, generating a plasma in the space between the upper and lower electrodes. The plasma thus generated is applied to the workpiece, whereby the target film formed on the workpiece is etched.
During the etching process, the reaction gas is introduced into the chamber through the holes of the upper electrode and is exhausted from the chamber through the exhaust pipe. Part of this gas reacts with the plasma and changes into a reaction-product gas. The reaction-produce gas is exhausted from the chamber through the exhaust pipe. That part of the reaction-product gas which has been generated at the periphery of the workpiece is immediately exhausted, but that part of the gas which has been generated at the center portion of the workpiece is hard to exhaust. Thus, less reaction-product gas accumulates on the edge portion of the workpiece than on the center portion thereof. As a consequence, the edge portion of the workpiece is etched faster than the center portion of the workpiece.